A SNAP-RING RETAINING DEVICE ADAPTABLE WITHIN A MATING GROOVE

Abstract

A retaining device or snap-ring for retaining a mating hub and drum within a transmission is provided. The device is insertable into a groove along the inner circumference of a circular flange and includes a main outer loop, an opening for dividing the snap-ring into two deflectable curvilinear portions and at least partially defined by a tabular extension projecting from each curvilinear member. The tabular extensions provide sufficient surface area for applying deflective or compressive force to the snap-ring and are contoured to facilitate use of a deflection tool. The snap-ring further comprises an externally-projecting secondary loop for reducing deflection force, or an internally-projecting secondary loop for increasing deflection force. The snap-ring may be used within a double-flange hub having a plurality of slots for facilitating insertion of the secondary loop and the tabular extensions within the flange groove.

Full Text

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SNAP-RING WITH ADDITIONAL LOOP
TECHNICAL FIELD
[0001] The present invention relates to an improved snap-ring retaining device
for use within a vehicle transmission.
BACKGROUND OF THE INVENTION
[0002] A circlip or snap-ring is a substantially circular or annular retaining
device having a break or opening which divides the ring into two interconnected
curvilinear members. The members may be deflected or flexed to facilitate insertion
into a mating groove. Snap-rings are typically formed, stamped, or otherwise
constructed from a relatively thin layer of metal which directs a retaining or
clamping force along the circumference or periphery of the snap-clip when properly
inserted into the groove. The directional force is most commonly used to retain or
clamp together various mating components.
[0003] The force vector imparted by the snap-ring varies with the type or style
of snap-ring that is used and the location of the ring relative to the parts retained or
mated. Two main styles of snap-ring are available: an internal snap-ring positioned
within a mating internal groove and used for applying outwardly-directed clamping
force, and an outer snap-ring positioned within a mating external groove for
applying inwardly-directed clamping force. Of these two main types of snap-ring,
internal snap-rings are of particular beneficial use within an automatic vehicle
transmission.
[0004] With an internal snap-ring, the ring is compressed or contracted by
deflecting the curvilinear beams or members of the ring and then inserted or
"snapped" into a continuous groove cut into an inner circumferential surface of a
drum, shaft, cylinder, or other component having an approximately circular cross
section. Once inserted into the groove, the snap-ring is then released or retracted
into its installed position, directing circumferential clamping force along the groove
wall within the relatively restricted space of the groove. In this manner a snap-ring

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may restrict or minimize any undesirable lateral or axial motion between two or
more mating parts, such as within a flange or flanges of a clutch hub and a mating
drum within a transmission clutch assembly.
[0005] The insertion and removal of a snap-ring during the transmission
assembly or build process may be relatively time or material intensive due to the
difficulty of accessing various confined areas within the housing. For instance, a
person installing a snap-ring must often insert or place the ring into an area having
limited accessibility or installation clearance, while simultaneously exerting a
substantial amount of force on the curvilinear beams of the snap-ring in order to
open or close the ring. The space and force limitations may be considerable enough
to necessitate the use of special-purpose capital equipment, potentially adding
substantial cost to the assembly process. Additionally, the requisite strength or
rigidity for higher-load applications may require a snap-ring formed from a
proportionately thicker layer of material, which in turn may lead to an undesirable
increase in overall axial space within a transmission case or other housing, resulting
in the need for a larger case and/or the re-arrangement of other components within
the system.
SUMMARY OF THE INVENTION
[0006] Accordingly, an improved retaining device is provided having a primary
or main loop, a variable-width or compressible opening dividing the main loop into
adjoining curvilinear beams or portions operable to exert a circumferential force
when inserted into a mating groove or channel, and an additional minor or
secondary loop connecting the curvilinear portions, and operable to modify the
deflection or compressive force required to compress or deflect the curvilinear
portions.
[0007] In one aspect of the invention, the opening comprises a plurality of
generally parallel tabular extensions, each extension having sufficient surface area
for applying compressive force to the main loop for flexing or bending of the
curvilinear portions to facilitate installation of the retaining device. The tabular

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extensions are further configured to prevent rotation of the snap-ring within the
mating circumferential groove.
[0008] In another aspect of the invention, a retaining device having an improved
compressive or deflection force is provided in which an externally-projecting
secondary loop reduces the compressive force required to compress or deflect the
curvilinear portions of the main loop, thereby facilitating the installation of the
retaining device.
[0009] In another aspect of the invention, a retaining device having improved
rigidity is provided in which an internally-projecting secondary loop increases the
compressive or deflection force required to compress or deflect the curvilinear
portions of the main loop, thereby providing increased rigidity to the main loop.
[0010] In another aspect of the invention, a circular flange assembly is
provided for use within a vehicle transmission, in which a substantially annular
retaining device having a main loop and a minor secondary loop is inserted into
continuous circumferential or peripheral groove in a flange wall, the main loop
having a plurality of tabular extensions configured to prevent rotation of the main
loop within the circumferential or peripheral groove.
[0011] In another aspect of the invention, a clutch assembly is provided for use
within a vehicle transmission, in which an improved snap-ring retaining device is
insertable in the mating grooves of a dual-flanged clutch hub and mating clutch
drum to thereby retain the clutch hub and drum.
[0012] The above features and advantages and other features and advantages of
the present invention are readily apparent from the following detailed description of
the best modes for carrying out the invention when taken in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIGURE 1A is a plan view of an improved snap-ring according to the
invention having an outwardly-projecting secondary loop;

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[0014] FIGURE IB is a plan view of an improved snap-ring according to the
invention having an inwardly-projecting secondary loop;
[0015] FIGURE 2A is a plan view of a clutch drum in combination with an
improved internal snap-ring;
[0016] FIGURE 2B is a side view of a double-flange clutch hub in combination
with an improved snap-ring;
[0017] FIGURE 3 A is a schematic illustration showing a load deflection of a
simplified straight or linear beam;
[0018] FIGURE 3B is a schematic illustration showing an exemplary load
deflection of a modified straight beam having the secondary outer loop of this
invention; and
[0019] FIGURE 3C is a schematic illustration showing a load deflection of a
modified straight beam having a secondary inner loop.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Referring to the drawings wherein like reference numbers correspond to
like or similar components throughout the several figures, there is shown in Figure
1A a substantially annular or circular snap-ring 10a comprising a primary or main
loop 20 having a width 11 and configured by a main radius 44 drawn from a main
center point 32. An outwardly-projecting minor or secondary extend loop 22a,
preferably circular in shape, is configured by a secondary radius 46a drawn from a
secondary center point 30a, the extend loop 22a projecting radially outward from the
circular periphery of main loop 20. A pair of tabular extensions or tabs 24a, 24b,
preferably aligned in a substantially parallel manner and positioned approximately
180° opposite secondary loop 22a, define a normal unflexed or "free state" break or
opening 26a in main loop 20. The unflexed opening 26a is represented by the
phantom or dotted-line profile in Figure 1A. Center points 30a, 32 are preferably
aligned along a main loop axis 38 bisecting main loop 20 and secondary extend loop
22a. Thus, main loop 20 has a first and second curvilinear beam portion 40, 42 being
at least partially flexible, compressible, or deflectable, by actuating tabs 24a, 24b

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disposed at the end of portions 40, 42, respectively. When curvilinear portions 40,
42 are deflected by the application of a contracting clamping force to tabs 24a, 24b,
a reduced-width or compressed opening 26b results, as shown by the solid line in
Figure 1A.
[0021] In a preferred embodiment, main radius 44 and secondary radius 46a are
proportionately related by a ratio of approximately 25:1, with compressed opening
26b, when substantially flexed or compressed, having a width approximately 0 to
5% of main radius 44. When curvilinear portions 40, 42 are in a "free state", i.e.
undeflected or unflexed, tabs 24a, 24b preferably form an unflexed opening 26a, as
shown by the phantom line in Figure 1A, with a relative angle of approximately 40°
between tabs 24a, 24b, although those skilled in the art will recognize that other
deflection angles and loop ratios may be adapted and modified as necessary
depending on the application. Tabs 24a, 24b are further preferably configured with a
notch or series of notches 25 being sized and/or shaped to fit a ring compression tool
(not shown), such as a pair of pliers, for assisting in compressing and inserting ring
10a into, for example, a flange groove in the wall of a clutch housing
[0022] Turning to Figure 2A, a circular drum 54, depicted herein as a
representative clutch drum, is shown with a captive snap-ring 10a as described
hereinabove. Snap-ring 10a is inserted into a channel or peripheral flange groove 50
positioned along the inner circumferential or peripheral surface 52 of the drum 54,
the groove represented in Figure 2A as a dotted line. A first window or slot 55a is
positioned at one end of drum 54 generally opposite secondary loop 22a, slot 55a
being appropriately sized to accept the elastically-deflectable tabs 24a, 24b of snap-
ring 10a to prevent relative rotation or spin of the snap-ring 10a within the flange
groove 50. To obtain the rotational balance as well as to accommodate insertion and
flexing of secondary outer loop 22a, the bottom or opposite end of the drum 54
likewise has a substantially similar and preferably identical slot 55b positioned
approximately 180° opposite slot 55a. Once compressed or deflected and inserted
into flange groove 50, and subsequently released, snap-ring 10a returns to a position
short of "free state" or unflexed opening 26a (See Figure 1A), and so exerts a

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continuous outward circumferential clamping force along the surface of groove 50,
thereby providing axial support and noise reduction between the mating parts, such
as, for example, between clutch drum 54 of Figure 2A and mating clutch hub 62 of
Figure 2B.
[0023] Clutch hub 62 of Figure 2B has a continuous outer circumferential
channel or hub groove 60 disposed between a first and second flange 63a, 63b.
Snap-ring 10a is inserted into groove 60 between flanges 63a, 63b and compressed
at tabular extensions 24a, 24b (see Figure 1 A) as described previously herewithin.
While holding snap-ring 10a in a compressed position, hub 62 is inserted into
mating clutch drum 54 (see Figure 2A). Tabular extensions 24a, 24b are held in
compressed position until hub 62 is fully inserted into clutch drum 54. Once the
snap ring 10a is aligned with flange groove 50, the tabular extensions 24a, 24b of
snap-ring 10a are released, and the snap-ring 10a partially opens or decompresses to
at least partially fill mating flange groove 50 (see Figure 2A) while remaining at
least partially within hub groove 60. Tabular extensions 24a, 24b snap into place
within slot 55a, thereby preventing relative rotation of the snap ring 10a within
grooves 50, 60. For example, in the case of clutch hub 62 of Figure 2B, the snap-
ring 10a would thereby retain the hub and drum, as would any splines on the mating
surfaces of clutch drum 54 and hub 62. For simplicity, mating splines are not shown
on surface 52 of clutch drum 54 of Figure 2A or on flanges 63a, 63b of hub 62 of
Figure 2B, which are the respective mating surfaces on which splines could be
employed. By utilizing the described double-flange design, the contact area or power
density between snap-ring 10a and flanges 63a, 63b is thereby doubled, which may
permit the amount and/or type of metal strengthening support components within the
transmission component, such as splining, to be reduced in number and/or otherwise
modified in appearance.
[0024] In an alternative embodiment of Figure IB, a snap-ring 10b has an
inwardly-projecting minor or secondary inner loop 22b having a center point 30b
and a secondary radius 46b. The primary advantages of a secondary inner loop are
twofold. First, by positioning a secondary inner loop 22b on the inside of main loop

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20, the outer dimension or periphery of snap-ring 1 Ob may be completely hidden
within a groove positioned within a circular wall of, for example, a clutch hub.
Additionally, in some circumstances installation space may be restricted or limited,
and consequentially, a secondary extend loop of the type shown in Figure 1A may
not fit properly within the flange. Second, a secondary inner loop 22b may be used
to enhance the rigidity of a snap-ring 10b, as an inwardly-disposed secondary loop
requires greater force to achieve a given amount of annular deflection than does an
outer-loop design, as discussed hereinbelow.
[0025] The deflection effect on a main surface due to the addition of a secondary
surface of various size and position may be explained by using the simplified linear-
beam profile of Figure 3A in which a straight beam 70a having a length LI is
attached to ground 74 and subjected to an applied load P. In this example, load P
imparts to beam 70a a deflection 8, in which 8 = P*(L1)3/(3*E*I). In this deflection
equation, variable E is Young's Modulus, commonly referred to as the modulus of
elasticity, with variable I being the moment of inertia. Those skilled in the art will
recognize that Young's Modulus E is a material-specific quantity, with a stiffer
material providing a reduced magnitude of deflection, while the moment of inertia I
varies with the shape of the beam profile.
[0026] Figure 3B modifies the single-beam design by adding an outwardly-
disposed minor beam 72a having a length L2. Under this modified configuration, the
force-deflection equation is modified to 8 = P * (LI + L2)3/(3*E*I). That is, the
addition of an outwardly-disposed minor-beam 72a increases deflection 8 for a given
load P. In designing a snap ring according to the invention, deflection can therefore
be customized by adapting a specific size and shape for the inner and outer loops, by
changing ring material, or by modifying the shape of the ring, as indicated by the
force-deflection equations.
[0027] By contrast, Figure 3C shows an inwardly-disposed minor beam 72b
having a length L2 equal to length L2 of Figure 3B. In this example, deflection δ =
P*(L1-L2)3/(3*E*I). The addition of minor-beam 72b therefore decreases deflection
8 for a given load P, that is, 72b imparts stiffness or rigidity to the beam as described

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previously herewithin. When this deflection effect is applied to a curved beam or a
beam of another non-linear shape, such as a snap-ring, the corresponding force-
deflection equations consider the radii of the inner and outer loops in determining
beam length and linear deflection. Note, however, that the general relationship of
inverse proportionality between deflection and both moment of inertia and Young's
Modulus, as illustrated in the simplified designs of Figures 3A-C, holds true
independent of beam shape and can be used by those skilled in the art to design a
snap-ring for a given application, in accordance with the teachings of this invention.
While the minor beams (secondary loop 22a, 22b of Figures 1A, IB) are preferably
circular, they may also take another suitable shape such as an oval or a parabola to
further increase or reduce the moment of inertia in the aforementioned manner.
[0028] While the best modes for carrying out the invention have been
described in detail, those familiar with the art to which this invention relates will
recognize various alternative designs and embodiments for practicing the invention
within the scope of the appended claims.

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CLAIMS
1. A snap-ring retaining device for use within a mating groove
comprising:
a main loop at least partially defining an opening having a
width which is reducable by compression of said main loop, wherein said opening
partially divides said main loop into adjoining first and second curvilinear portions
operable to retain said main loop within said mating groove; and
a secondary loop connecting said first and second curvilinear
portions and operable to affect the compressive force required for installing and
releasing said main loop with respect to said mating groove.
2. The snap-ring retaining device of claim 1, wherein said
opening is further defined by a plurality of generally parallel clampable tabular
extensions each having sufficient surface area for applying compressive force to said
main loop for flexing of said curvilinear portions, said tabular extensions being
further configured to minimize rotation of said device within said mating groove.
3. The snap-ring retaining device of claim 1, wherein said
secondary loop is sufficiently externally-projecting to reduce the compressive force
required to flex said curvilinear portions.
4. The snap-ring retaining device of claim 1, wherein said
secondary loop is sufficiently internally-projecting to increase the compressive force
required to flex said curvilinear portions.
5. The snap-ring retaining device of claim 1, wherein the radius
of said main loop and the radius of said secondary loop are proportionately related
by a ratio of approximately 25:1.

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6. The snap-ring retaining device of claim 1, wherein the width
of said opening is approximately 0 to 5% of the main radius of said main loop when
said opening is fully compressed.
7. A circular flange assembly for use within a vehicle
transmission, the assembly comprising:
a drum having a flange wall with a peripheral main groove;
and
a substantially annular retaining device having a main loop
including an opening having a width which is reducable by compression of said
main loop, said opening at least partially separating said main loop into a pair
curvilinear portions operatively connected by a minor secondary loop;
wherein said retaining device is at least partially flexible and
insertable into said main groove for applying an outward clamping force.
8. The assembly of claim 7, including a first flange slot and
a second flange slot positioned substantially opposite said first slot, wherein said
main loop further comprises a plurality of clampable tabular extensions at least
partially defining said opening and configured to be insertable into one of said slots
to thereby minimize rotation of said retaining device within said main groove.
9. The assembly of claim 7, including a first flange slot and
a second flange slot positioned substantially opposite said first slot, wherein said
secondary loop is insertable into one of said slots, each of said slots providing
sufficient open surface area for the flexing of said secondary loop therewithin.
10. The assembly of claim 7, wherein said secondary loop is an
internally-projecting inner loop operable to increase the compressive force required
to flex said curvilinear portions.

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11. The assembly of claim 7, wherein said secondary loop is an
externally-projecting extend loop operable to reduce the compressive force required
to flex said curvilinear portions.
12. The assembly of claim 7, wherein the radius of said main loop
and the radius of said secondary loop are proportionately related by a ratio of
approximately 25:1.
13. The assembly of claim 7, wherein the width of said opening is
approximately 0 to 5% of the main radius of said main loop when said opening is
fully compressed.
14. A clutch assembly for use within a vehicle transmission, the
assembly comprising:
a first and second clutch hub flange having a continuous
peripheral hub groove therebetween;
a clutch drum having a flange wall with a peripheral flange
groove; and
a snap-ring retaining device having a main loop including an
opening having a width which is reducable by compression of said main loop, the
opening at least partially separating said main loop into a pair of operatively
connected curvilinear portions, and a minor secondary loop connecting said pair of
said curvilinear portions for facilitating flexing of said curvilinear members;
wherein said clutch hub is insertable into said clutch drum,
and wherein said snap-ring retaining device is insertable within both of said hub
groove and said flange groove to thereby retain said clutch hub with said clutch
drum.

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15. The clutch assembly of claim 14, wherein said secondary loop
is an internally-projecting inner loop operable to increase the compressive force
required to deflect said curvilinear portions.
16. The clutch assembly of claim 14, wherein said secondary loop
is an externally-projecting extend loop operable to reduce the compressive force
required to deflect said curvilinear portions.
17. The clutch assembly of claim 14, said clutch drum including a
first flange slot and a second flange slot positioned approximately opposite said first
slot, wherein said main loop comprises a plurality of tabular extensions at least
partially defining said opening and insertable into one of said slots to thereby
minimize rotation of said snap-ring within said hub groove and said flange groove.
18. The clutch assembly of claim 14, wherein the radius of said
main loop and the radius of said secondary loop are proportionately related by a
ratio of approximately 25:1.
19. The clutch assembly of claim 14, wherein the width of said
opening is approximately 0 to 5% of the main radius of said main loop when said
opening is fully compressed.
20. The clutch assembly of claim 17, including a secondary loop
which is insertable into one of said slots to thereby allow flexing motion of said
secondary loop.

A retaining device or snap-ring for retaining a mating hub and drum
within a transmission is provided. The device is insertable into a groove along the
inner circumference of a circular flange and includes a main outer loop, an opening
for dividing the snap-ring into two deflectable curvilinear portions and at least
partially defined by a tabular extension projecting from each curvilinear member.
The tabular extensions provide sufficient surface area for applying deflective or
compressive force to the snap-ring and are contoured to facilitate use of a deflection
tool. The snap-ring further comprises an externally-projecting secondary loop for
reducing deflection force, or an internally-projecting secondary loop for increasing
deflection force. The snap-ring may be used within a double-flange hub having a
plurality of slots for facilitating insertion of the secondary loop and the tabular
extensions within the flange groove.